Separation of oxygen-containing organic compounds from aqueous mixtures



BRUNR ET Ax.

F. H. SEPARATION OF OXYGEN-CONTAINING ORGANIC.

July 29, 1952 coMPouNDs FRoM AQUEous MIXTURES Filed Aug. :51, 1946 INVENToRs Frank H. Bruner Han/ara' l( Hess BY 'George Arno/d B mi ww Patented July 29,` 1952 k 2,605,27c SEPARATION F OXYGEN-CONTATNING FORGANIC COMPOUNDS FROM AQUE- oUs-MixrUREsy Frank' H. Bruner, Fishkill,y Howard y. Hess,H 'y

Beacon, and George B. Arnold, .Glenham, N. Y;, 'O assignors to' The yTexas Company,NeW;Yor N; Y., a corporation of Delaware f. i

Application August 31, 1946,'seria No. 694,403 l This invention relates" tothe separation of oxygen-containing organic compounds from aiuous mixtures containing them such as obtained from the conversion of carbon monoxide andhydrogen 'into hydrocarbons, oxygen-con-r taining compounds and the like.

T hekinventio-n broadly contemplates separating oxygen-containing'compounds such as aliphatic alcohols from aqueous mixtures containing them by extraction with ai'hydrocarbon 'or hydrocarbon fraction such 'as 4naphtha atelevated tempe'rature and preferably. inthe liquid phasesuch that the hydrocarbon exerts preferential solvent action upon such compounds'.` A solventerich phase," is obtained" consisting essentially of hydrocarbon 'solventand dissolved oxygen-contain-` in'g'compoundsand a water phase consisting essentially of Water. Organic acids, if present Ain the 'feed mixture, remainvmainly in the Water phase.

The solvent-rich phase is separated and subsequentlytreated with a secondary solvent, ad- V'antageously a solvent having substantially complete'solvent action upon aliphatic alcohols and being substantially immiscible with hydrocarbons at lordinary temperatures, for example, in the range of 70-150" F. The treatment with'the secondary solvent is` made under conditions so as to form a secondary extract or solvent-rich phase i and Water.

solvent for re-use.- vThe hydrocarbon-rich phase l can Y be separately treated to remove small amounts of secondary solvent that may be asso.v

ciated With it afterewhich the hydrocarbons or any lportion thereof can be used for treating additional freshfeedmixture. .Y f

-Ethylene glycol isv an effective secondary solvent-for effectingliquid-liquid extraction of oxygent-containing compounds from hydrocarbons,

although-other olefin glycols including polyolefinr y and fketonesf from'` aqueous vmixtures with a hydrocarbon liquid such as petroleum naphtha and the normally liquidv hydrocarbons naphtha and higher boiling hydrocarbons'gpro-,i duced in the synthesis of hydrocarbonswfrom. carbon monoxide and hydrogen.

It is contemplated that synthesis hydrocarbons solvent-for this purpose.

Under'liquid phase cond1tions andrat ate'm;

perature 'in the range of about200-300-;F.,; naphtha hydrocarbons such as obtainedv from the? synthesis reaction exert an unexpectedly-high partition veffect between Water ontheone" hand and aliphaticV alcohols,` aldehydes and vlzetoneson` the other. For example, when countercurren'tly: extracting an aqueous mixturecontaining'about 7 or 8% by weight of primary aliphatic'alcohols having from 2 to 8 or more carbon *atoms-:pen moleculev at a Vtemperature of '200fl-:F.- with naphtha in the proportion o'f about 1 to2 volumes of naphthaper volume of aqueousmixture,'sub:- stantially all of the alcohols are dissolved.'t in :the hydrocarbon solvent and c-an be 'removedfrom the extraction zone inthe solvent p'haseQleaying a Water phase consisting essentially of--water-.

.-Thefinvention is particularly useful 'as rapplied to vthetreatment of aqueous 'mixtures obtained inthe conversion of carbon monoxideland hydrcleI gen by contact with a synthesiscatalyst. 1 `*Ilrie product of the synthesis reaction usually coin-' prises hydrocarbons, oxygenated hydrocarbons The oxygenated y hydrocarbons y in# clude aliphatic alcohols, aldehydes, ketonesfand a small amount of organic acids; Uponicooling of the synthesis product, separation intoij'aliguid hydrocarbon phase and a liquid waterphasecc` curs. The Water phase usually contains the fore'- going oxygenated YAcompounds*` in substantial amount; the compounds ranging mainly fro'rr'rg-Zy to 8 or more carbon atoms per molecule. *f

In accordancewith this invention; the aforesaid Water phase is.extracted-with';naphtha 'at a temperature Aof4 about 200 Randi und 4*a pressure of-.about` 150 pounds or;higher:fls a v*result of f this extraction there is j obtained fa solvent-rich phase. comprising aliphatic` alcohols,

4 aldehydes, and ketones dissolved` in naphtha.

anda Water phase consisting essentially of Water and organicA acids. -Small amounts.L of ketones and aldehydes may remain in the lWater phase.; These phases yare separated. ,'lhe''acids i' il including Synthesis; naphth-a which consists essentially of aliph'atia` hydrocarbons andwhich usually is substantially#v free from aromatic and naphthenicfhydrocarri` bons has'been Afound effective for thispurpose;

as previously referred to so as to effect separation of the alcohols from the `hydrocarbon sol-A vent. The secondary extract phase comprising alcohols dissolved in secondary solvent can be then subjected to fractional distillation or `suchV other treatment as necessary in order to recover the individual'alcohols therefrom.Y

For example this secondary extract phase may b'e-f passed to a distillingcolumn or columns wherein it is subjected to distillation to produce therefrom C2 and C3 alcohols in the form of their'azeotropes with Water, andCfr-C alcohols in substantially anhydrous form. Residual water retainedin the alcohol solutions provides that required for azeotrope formation,V The residual fractioncontainin'g Cf 'andghigher molecular weight alcohols as .well as rsecondary) solvent can be subjected `to"separate steam vdistillation so as to separate these higher alcohols; from the solvent which latter can Vbe recycled to the secondaryV solvent extraction step. The distillate from the distillation will include, methyl alcohol inazeotro'pe. form'if present in the secondary extract phase. 'w A Y Y l Reference'will nowbe rmade'to the accompanying drawing comprising a, flow diagram illustratingthe application of the process of the invention tothetreatment of an aqueous mixture i-obtained' from: theconversion of carbon monoxideand hydrogen. -v Y Y I" indicated in the drawing, carbon monoxide and :hydrogen-rin the proportion, for example, of 2`1mols'.oi-hydrogen to 1 mol of carbon monoxide `andobtained vfrom-"a source not vshown are Vpassed through a conduit I to a conventional synthesis unit; 2. 1n the synthesis unit the reactants. maybe subjected to contact with a synthesisxcatalystin'the form of a uidized mass isolid'particles or powder. Advantageously the catalyst' comprises iron,although other synthesis catalystsV Vcomprising cobalt or nickel may be used. Y' The synthesis `catalyst may comprise alkali; metals or metal compounds. and oxides of*` thorium, jmagnesium and aluminum as promoters.'V4 Y l. Y Y For-example, an' effective iron catalyst containsaboutz to3% alumina and about 0.1 to 3.0% `alkali (expressed `as potassium oxide). Thel synthesis reaction .with such a catalyst, operating-forhthe production of hydrocarbons mainly, is usually-carried out at a temperature of aboutl500-650". F, and `under a pressure of abut200-.p'oundsh- V Y; -An feflluent' streamj of synthesis reaction mixturefis'removed througha conduit 3 and passed through-a; cooler"` 4 wherein its Ytemperature mat7 be reducedtoatniospheric or to about G-150 F. wlthoutsubstantial reduction in pressure. The resulting. cooled mixtureis'passed through a coduitj to aseparating vessel 6. In the separator-,.threephases form: V(1) `a gas phase comprisin'glunreacted jgasfcarbon dioxide and norinallyjgaseous hydrocarbons such as methane, ethane, propane, butane, etc.,Y (2) a hydrocarbonrich phase containing some oxygenated compounds including aliphatic alcohols mainly of` two or more carbon atoms per molecule, andi (3) a water-rich phase comprising water, ali-v phatic alcohols, faldehydes, ketones ,and organici acids. l' Y, Y These phases are separately withdrawn fromthe separator 6. The gas phase may be discharged through conduit 'I and may be recycled v .in part to the synthesis unit 2. This gas phase may also be treated to remove carbon monoxide, hydrogenv and carbon dioxide for recycling to the Ysynthesis unit.

The water phase" is continuously removed from the separator E through a conduit 8 to an extraction tower S. A heat exchanger H, inserted in the conduit 8, serves to raise the water phase Vto a temperature of about 200 to 300 F. prior to its introduction into the extraction tower 9. In

the extraction tower 9 it' is subjected to countercurrent contact with naphtha or higherboiling hydrocarbons obtained ina subsequent step of the process. When naphtha is used as the extracting medium, the extraction is carried out at a temperature of about 200-300" F. Slightlyv lower temperature may be used, as for example 175 F., when gas oil is used as the extracting medium. This extraction is.. carried outw'under pressure in the range to V30,0fpounds and'sufciently elevated to maintain liquid phase condi-. tions within the extraction tower. The extractionv pressure may be substantially the sar'ne'asV that prevailing in the synthesis'unit. 1

The hydrocarbon solvent is introduced to the lower portion of the Y,tower and rises therethrough countercurrently, to the downwardlyrlfowirlg feed mixture'. As a result ofthe extractive treatment, a stream of water substantially free 'fromalcohols", aldehydes and ketones is discharged from the bottom of the 'towerA through a conduit lil. This water will retain at least the bulk ofthe acids present in the water phase stream flowing through the conduit 8. Thus-the organic'acids infthisfY Water stream, taken as acetic` acid, may be` the range about 1 to,3% by weight/basis the water:

Ypipe I5 and thus commingled with the fluid stream flowing through the conduit I3. The bisulte solution is added in ysuflicient amount and' of suitable concentration to react with aldehydes and ketones present inl ther mixture flowing through the conduit I3 and form addition compounds. The resulting r:mixture containing addition compounds ows into the vessel i4 wherein the addition compounds separate as anadueous layer. This aqueous layer is drawn oi through a pipe I6 and subjected to such furthertreatment as may be desired in order to recover thev aldehydes and ketones. These aldehydes and ketones may amount to about 11/2 to 2 volume per cent of the combined Water phase and hydrocarbon phase leaving the separator 6;

The alcohol-containing hydrocarbon-rich phase forming in the vessel Iltis continuously'drawn oli through the conduit I'Iand if 'desired' passed to a fractionator 20 wherein the mixture may be separated intoxa distillatenfraction boiling within: 'the'. range of. fnaphtha, for example .up .to about;1400" F., and a residual fractionrcomprising higher :boiling material. Both fractions lwill thus comprise. mixtures of'Y hydrocarbons and alcohols.. AA distillate fraction is vremoved'fromlthe; frac-I tionator' through. conduit 2| and ypassed' Ytorasecondary extractor22. f

As"indicate'djthe fractionator 20 may-xbefbypassed,in whichcase, the total hydrocarbon-alcoholmixture flowing-through the conduit I1 may be ,diverted through conduit IIa,l communicating with conduit 2| and thus passing directly to the secondary extractor 22.

In the secondary extractor the enteringmixture of hydrocarbons and alcoholsissubjected to countercurrent contact Witha solvent liquid such as ethylene glycol. Ilfresolvent is introducedjto. the top of the extractor through conduit 2,3 xto which reference will be: made later. Conditions are maintained Ywithin the extractor so that.- the solvent exerts substantially lcomplete solvent action upon the, alcohols and substantially no, or only very little, solvent action upon; the hydrocarbons.

The secondary solvent may be charged at the rate of about 1 to 11/2 volumes' per volume of feed mixture entering through the conduit 2|. The extraction may be effected at a temperature in the range of 'l0-150 F. As a result, there is obtained from the top of the extractor, a hydrocarbon-rich phase substantially free from oxygen-containing compounds and containing a relatively small amount of solvent. This hydrocarbon-rich phase is continuously removed through a conduit 24 to a washing tower 25 wherein it is scrubbed with water so as to extract residual solvent therefrom. The residual solvent dissolved in water is removed through conduit 26 and may be passed to a distilling means or other recovery means adapted to recover the solvent from the water.

The washed or scrubbed hydrocarbons are removed and conducted through conduit 21. A portion thereof is diverted through conduit 28 and used as the solvent in the aforementioned extraction tower 9. The hydrocarbons are raised to temperature of about 200 to 300 F. in a heat exchanger 29, situated in the -conduit 28, prior to their use in the extraction tower 9. The portion not so recycled is passed to a product recovery or product treating system not shown. For example, this portion may be subjected to treatment with clay, bauxite or other contact material for the purpose of converting it into products of desired characteristics including gasoline of high antiknock.

Referring again to the fractionator 20, the gas oil fraction removed therefrom as a residual fraction is conducted through a conduit 30 and may be passed to an extractor 3| similar to the extractor 22. In this extractor the mixture of oi] and alcohols is likewise extracted with a selective solvent such as used in the extractor 22. Conditions of operation in the extractor 3 may he substantially similar to those in the extractor 22 such as to eiect Substantially complete removal of alcohols from the gas oil.

.A gas oil stream substantially free from oxygen-containing compounds and containing a relatively small amount of solvent is removed from the top of the extractor 3| through a conduit 33 to a scrubber 34 wherein it may be washed with water to remove the residual solvent therefrom, the residual solvent andiwater being discharged through a pipe 35.

.The washed gas,V oil lstream is discharged through apipe 36. the event that gas oil is` being used as the solvent in theextractor 9,; a portionv of the gas owing through pipe 36 may be. diverted through pipe 31,1com'municating with the previously mentioned pipe 28 bywhich the hydrocarbon solvent is conducted Ito `the tower- 9. In this event, the 'stream leavingv they top-of the towerthrough `pipe, I2 is diverted through pipe 2a.to the'extractor 3|.

From thebottomof both extractors 22 and 3| are Withdrawn extract phasemixtures comprising alcohols .dissolved in the secondary solvent. The secondary extract phase from the tower 3| may be 'separatelytreated or may be conducted through a conduit 4B, communicating with a conduit '4| through which the secondary extract phasefrom the extractor V22 is withdrawn., Both streams then pass to an alcohol recovery unit 42.

The recovery unit 42 may comprise a plurality of distilling columns and auxiliary apparatus adapted to effect separation of the individual alcohols from the secondary solvent-alcohol feed mixture. y

For example, there may be obtained from the recovery unit 42, the following products, the per cent yield being on the basis of total hydrocarbon phase and waterV phase leaving the separator 6: f

Volume per cent Ethyl alcohol-water azeotrope 10 N-propyl alcohol-water azeotrope 2.6 N-butyl alcohol (anhydrous) 0.87 N-amyl alcohol (anhydrous) 0.80 N -hexyl alcohol (anhydrous) 0.63 N-heptyl alcohol (anhydrous) 0.55 Higher alcohols (anhydrous) 0.63

While not specifically mentioned, it is contemplated that the countercurrent extraction operations carried out in the extractors 9, 22 and 3| may involve employment of suitable temperature gradients through the extraction towers and extract recycle. The solvent dosages may vary from those mentioned. Temperatures may vary from those mentioned, while the pressures are maintained suflicient for liquid phase operations.

While the foregoing synthesis reaction has been described with reference to the production of hydrocarbons as well as oxygen-containing compounds, it is contemplated that the synthesis operation may be carried out under conditions adapted mainly for the production of oxygencontaining compounds. Synthesis reaction temperatures may range from 20D-'700 F. and pressures from atmospheric to several hundred pounds or more. Moreover the synthesis reaction is not necessarly conned to the employment of a fluidized mass of synthesis catalyst. In other words, the synthesis catalyst may be used in other forms, as for example in the form of a stationary bed, a moving bed or a suspension in the reactants.

Moreover, the extracting operations of the `present invention are not limited to the treatment of alcohol-Water mixtures obtained from the conversion of carbon monoxide and hydrogen but may be employed to treat mixtures derived from other sources.

While ethylene glycol has been mentioned as a suitable secondary extraction solvent, it is contemplated that other solvents may be used including high molecular Weight compounds such as those which may be produced in the synthesis unit and may be recovered from the recovery unit 42.

It is contemplated that the solvent-rich phase leaving the top of the extraction tower 9 can be separately extracted with secondary solvent instead of being mixed with the hydrocarbon phase mixture leaving the separator 6. Such separate treatment would be in order where the mixture of water and oxygen-containing compounds is obtained from an extraneous source. For example, when the solvent-rich phase vfrom theextraction tower 9 is separately treated with a secondary solvent, and the resulting secondary extract phase passed to a recovery unit such as the recovery'unit 42, the following yields may be obtained basis feed mixture to extractor 9:

Volume per cent Ethyl alcohol-water azeotrope 10 N-propyl alcohol-water azeotrope 3 N-butyl alcohol-water azeotrope 1 Higher molecular weight alcohols (anhydrous) 5 Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

We claim:

A process for separating non-acidic aliphatic water-soluble oxygenates containing up toabout eight carbon atoms from acidic aliphatic watersoluble oxygenates,` which comprises subjecting an aqueous solution containing said acidic and non-acidic oxygenates to countercurrent contact with a hydrocarbon solvent at a temperature of about 175'to 300 F. and under pressure sufficient to maintain substantially liquid phase conditions whereby there is obtained a hydrocarbon extract phase containing non-acidic oxygenates and a raflinate phase containing said acidic oxygenates.

FRANK H. BRUNER. HOWARD V. HESS. GEORGE B. ARNOLD.

REFERENCES CTED The following references areof record 1n the file of this patent:

Y UNITED STATES PATENTS Number Name Date 1,870,816 Lewis Aug. 9, 1932 2,083,125 Scheuble June 8, 1937 2,274,750 Soenksen et al Mar. 3, 1942 2,410,642 Farkas et a1 Nov. 5, 1946 2,446,231 Johnson Aug. 3, 1948 2,476,788 White July 19, 1949 OTHER REFERENCES Fischer: Conversion of Coal into Oil, pub. b Ernest Benn Ltd., London (1925), 241-6. 

